ESTRO 2021 Abstract Book

S1027

ESTRO 2021

resection, organ-sparring transanal tumorectomy or more extensive surgery for 107 (69%), 25 (16%) and 23 (15%) patients respectively. There was no post-operative death and 86 patients (56%) had no postoperative complications (Table 1) . Severe surgical morbidity occurred in 37 patients (24%), 16 patients (21%) in IMRT arm versus 21 patients (27%) in 3D-RT arm (p=0.628). Acute grade >2 gastro-intestinal (GI) toxicity occurred in 11 patients (7%): 1 patient (1%) with IMRT versus 10 patients (13%) with 3D-RT (p=.006) (Table 2) . There was more grade > 2 diarrhea in patients receiving induction CT and among those patients, there was less diarrhea with IMRT (n=1, 3%) compared with RT-3D (n=7, 24%) (p = 0.017). Among the patients were treated by anterior resection, 52 LARS questionnaires could thus be collected with a median interval between surgery and the LARS evaluation of 1.5 years in the IMRT arm, versus 5 years in the 3D-RT arm (p < 0,001). Eighteen patients (35%) reported major LARS: 6 (27%) in the IMRT arm and 12 (40%) in the 3D-RT arm without significant difference.